From that page, I see:
NOTE: This wrapper is not verified by, affiliated with, or supported by Authy nor Twilio.
IMPORTANT: This app will reach their End-of-Life on March 19, 2024 (more info in FAQ link).
Note the date.
Also note the flatpak’s setup file points to the physical snap package. If I am reading the yaml file correctly, the flatpak is simply downloading this and extracting the contents to where it would go as a flatpak. The error is that the snap package no longer exists. Note the EOL date…
The link to the Authy snap leads to a 404
This isn’t a Discover or KDE issue.